Onyx is a banded variety of the oxide mineral chalcedony. Agate and onyx areboth varieties of layered chalcedony that differ only in the form of the bands:agate has curved bands and onyx has parallel bands. The colors of its bandsrange from white to almost every color (save some shades, such as purple orblue). Commonly, specimens of onyx contain bands of black and/or white.

Historicuse : It has a long history ofuse for hardstone carving and jewelry, where it isusually cut as a cabochon or intobeads. It has also been used for intaglio and hardstone cameo engraved gems, where the bands make the image contrast with the ground. Someonyx is natural but much of the material in commerce is produced by thestaining of agate.